How does the Roth conversion optimizer work?

It searches conversion schedules and returns one verified near-optimal against a brute-force oracle in the test suite, while respecting tax brackets, IRMAA tiers, the ACA subsidy cliff, and future required minimum distributions.

How much can Roth conversions save?

It depends on your tax-deferred balance and how much bracket room you have. The optimizer maximizes the money you keep after every tax is paid, and shows that figure alongside the lifetime tax saved for your own plan — the number, not a rule of thumb.

Will conversions trigger IRMAA or cost me ACA subsidies?

The optimizer is IRMAA- and ACA-cliff aware. It factors the two-year IRMAA lookback and the subsidy cliff into the schedule instead of ignoring them.

Yes, and no account is needed. It is private by default — the optimizer runs in your browser.

Sample data

This is an example household so you can see the tool working.

Roth Conversion Planner

See how much you could save by converting at the right pace

Money you keep

+$174K

more after tax at age 95 than converting nothing

Tax now

$89K

all-in, in your conversion years

Converting $540K between ages 62 and 74 costs $66K in tax now, and moves that money somewhere it — and everything it earns from here — is never taxed again. It cuts your tax-deferred balance at age 95 to $654K — down from $1.2M — but does not empty it.

How much to convert

74% of the possible gain, for 38% of the full tax bill

Diminishing returns

How this is calculated

Why “Tax now” is bigger than the tax on the conversions — that number is only the income tax on the conversions themselves: what shows up on your tax returns, and what the yearly schedule adds up to. This figure also counts everything a conversion sets off in the same year — higher Medicare premiums, extra investment tax, lost health-insurance subsidies. The money you keep has already paid all of those, so the cost side includes them too.

Where the zones split — Up to Efficient, each new $1 of tax adds at least $0.50 of estate; past it, less. Every stop up to Optimal still adds net money — at a shrinking rate.

What this rests on — Converting more prepays more tax on the strength of today’s assumptions.

Lifetime tax saved

$122K

over the whole plan

Converted

$540K

scheduled across your conversion years

Conversion years

13 (ages 62–74)

before required distributions begin

Tax-deferred at age 95

$654K

was $1.2M

this plan does not empty it

What you keep

Tax-Deferred

Roth

RMDs begin (Pat), age 75

RMDs begin (Lee), age 73

With this strategyIf you convert nothing

Roth conversions shift money out of tax-deferred and into Roth. RMDs begin at age 75 (Pat) and 73 (Lee). All balances are in today’s dollars.

Why this works

Tax per year

Tax this strategy pays

Tax if you convert nothing

You pay more tax in the conversion years and less afterwards. Everything is in today’s dollars.

IRMAA: clear every year

Efficient is the last point on your own curve still earning $0.50 of estate per $1 of prepaid tax; it is offered only when it saves at least 20% of the conversion tax. How this is calculated

Roth Conversion Schedule

Age	Conversion	Federal Bracket	Federal	State	ACA/IRMAA	Tax Cost
62	$57KWhy this amount: Stops just below the ACA subsidy cliff — 400% of the federal poverty level.	10% →4%	$2K	$0	+$28K	$2K
63	$29KWhy this amount: Stops just below the ACA subsidy cliff — 400% of the federal poverty level.	10% →0%	$0	$0	+$10K	$0
64	$23KWhy this amount: Stops just below the ACA subsidy cliff — 400% of the federal poverty level.	10% →0%	$0	$0	+$11K	$0
65	$37KWhy this amount: Lands in the 12% bracket, $18.2K below the 22% edge.	12% →12%	$4K	$0	—	$4K
66	$54KWhy this amount: Lands in the 22% bracket, $81.4K below the 24% edge.	22% →18%	$10K	$0	—	$10K
67	$31KWhy this amount: Lands in the 12% bracket, $3.9K below the 22% edge.	12% →12%	$4K	$0	—	$4K
68	$44KWhy this amount: Lands in the 22% bracket, $100.7K below the 24% edge.	22% →15%	$7K	$0	—	$7K
69	$45KWhy this amount: Lands in the 22% bracket, $99.6K below the 24% edge.	22% →15%	$7K	$0	—	$7K
70	$46KWhy this amount: Lands in the 22% bracket, $97.8K below the 24% edge.	22% →15%	$7K	$0	—	$7K
71	$48KWhy this amount: Lands in the 22% bracket, $96.0K below the 24% edge.	22% →16%	$7K	$0	—	$7K
72	$51KWhy this amount: Lands in the 22% bracket, $91.1K below the 24% edge.	22% →16%	$8K	$0	—	$8K
73	$36KWhy this amount: Lands in the 12% bracket, $11.0K below the 22% edge.	12% →12%	$4K	$0	—	$4K
74	$38KWhy this amount: Lands in the 12% bracket, $8.3K below the 22% edge.	12% →12%	$5K	$0	—	$5K
Total	$540K		$66K	$0	+$49K	$66K